1. Field of the Invention
The present invention relates to a control device of an internal combustion engine, more specifically, a control device of an internal combustion engine which distinguishes and detects an abnormal combustion generated in an internal combustion engine, for example, into an abnormal ignition such as a knock, a pre-ignition or a post-ignition, thereby permitting the control suitable for each abnormal combustion to perform.
2. Background Art
Generally, it is known that, when a knock as one abnormal combustion of the internal combustion engine is generated during operation of the internal combustion engine, a vibration of a natural frequency band is generated in the internal combustion engine depending on a configuration of the internal combustion engine or a vibration mode of the knock. However, from the related art, a control device of an internal combustion engine is suggested which detects the knock generated in the internal combustion engine using a vibration sensor and performs the control of the internal combustion engine based on the detection value. The device of the related art measures a vibration intensity of the natural frequency band generated in the internal combustion engine to detect the knock, and performs a retard correction of the ignition timing of the internal combustion engine to suppress the knock.
As a specific method of measuring the vibration intensity of the natural frequency of the internal combustion engine, a method of inputting an output of a vibration sensor via a band pass filter constituted by an analog circuit to a peak hold circuit and measuring the vibration intensity based on the peak hold value after the band pass filter obtained by the peak hold circuit (for example, see Patent Document 1), a method of performing a digital signal processing such as FFT (Fast Fourier Transform) on the output of the vibration sensor and measuring the vibration intensity by the spectrum value of the natural frequency (for example, see Patent Document 2) or the like are suggested.
In the internal combustion engine, after a spark ignition by an ignition plug, a flame spreads around the ignition plug. However, at this time, a phenomenon, in which an end gas as an unburned gaseous mixture located far from the installation position of the ignition plug is pressed against a wall surface of a piston or a cylinder, comes to have a high temperature and a high pressure, and is self-ignited, is considered to be a knock as an abnormal combustion. When the knock is generated, a shock wave is generated, whereby the vibration or a metallic sound of a block of the internal combustion engine is generated.
Meanwhile, it is known that, as the abnormal combustion generated in the internal combustion engine, besides the knock mentioned above, the abnormal ignition called pre-ignition or post-ignition also exists. Furthermore, it is considered that, in the abnormal ignition called pre-ignition or post-ignition, there is a case (hereinafter, referred to as a heat source self ignition) where a deposit in the ignition plug or a pipe becomes a high temperature, becomes a heat source and leads to the ignition, a case (hereinafter, referred to as a compression self ignition) where the gaseous mixture comes to have a high temperature and a high pressure in a compression stroke when a compression ratio is high, and leads to the self ignition, or the like. Even in the case of the abnormal ignition as the abnormal combustion, in some cases, the pressure in the pipe or the vibration, the metallic sound of the internal combustion engine block or the like is involved.
Among the abnormal ignitions mentioned above, the abnormal ignition generated before a regular flame ignition is called a pre-ignition, and the abnormal ignition generated after the regular flame ignition is called a post-ignition. Since the abnormal ignitions are phenomena that perform the combustion regardless of the ignition timing, in some cases, the abnormal ignitions are not suppressed even when retarding the ignition timing. The abnormal ignition as the abnormal combustion is generally known (for example, see, non-Patent Documents 1 and 2), when the abnormal ignition is generated, an unpleasant metallic sound is generated or variation in the output of the internal combustion engine or the like is generated, and in an extreme case, the internal combustion engine may be damaged.
When the abnormal ignition such as the pre-ignition or the post-ignition mentioned above is generated, since the abnormal vibration of the internal combustion engine may be involved, a method of implementing the detection of the abnormal ignition by applying the knock detection method mentioned above is suggested. As the method, a method (for example, see Patent Document 3) of deciding an occurrence of the abnormal ignition based on a time difference between the ignition timing and the abnormal vibration occurrence timing or a method (for example, see Patent Document 4) of deciding an occurrence of the abnormal ignition when a state continues where a time interval, while the abnormal vibration equal to or greater than a predetermined level is not detected, is shorter than a predetermined interval, is suggested.